netdev - Re: [PATCH net-next 0/5] sched: convert queues to single-linked list

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Message-Id: <20160919.014744.226583519665969413.davem@davemloft.net>
Date:   Mon, 19 Sep 2016 01:47:44 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/5] sched: convert queues to single-linked
 list

From: Florian Westphal <fw@...len.de>
Date: Sun, 18 Sep 2016 00:57:29 +0200

> During Netfilter Workshop 2016 Eric Dumazet pointed out that qdisc
> schedulers use doubly-linked lists, even though single-linked list
> would be enough.
> 
> The double-linked skb lists incur one extra write on enqueue/dequeue
> operations (to change ->prev pointer of next list elem).
> 
> This series converts qdiscs to single-linked version, listhead
> maintains pointers to first (for dequeue) and last skb (for enqueue).
> 
> Most qdiscs don't queue at all and instead use a leaf qdisc (typically
> pfifo_fast) so only a few schedulers needed changes.
> 
> I briefly tested netem and htb and they seemed fine.
> 
> UDP_STREAM netperf with 64 byte packets via veth+pfifo_fast shows
> a small (~2%) improvement.

Series applied, thanks Florian.